1. Field of the Invention
This invention pertains to dental handpieces generally, and more particularly to a turbine spindle assembly in which the loosened chuck nut is retained and does not experience undesired movement during changing of burs or drill bits.
2. Description of the Background Art
Dental handpieces for supporting drills and burs generally comprise multi-component arrangements wherein a turbine rotor or spindle is driven by compressed air or mechanical means. The turbine or spindle imparts rotational motion to the drill bit or bur. Currently available dental handpieces generally have means for holding a drill bit or bur in the handpiece in the form of a chuck nut and threaded spindle assembly. For example, U.S. Pat. No. 4,198,754, incorporated herein by reference, discloses a dental turbine spindle assembly in which a spindle with turbine rotors is rotatably mounted within a housing, and drill bits and burs are interchangeably attached by inserting in a bore within the spindle, and tightening or loosening a chuck nut which threads onto the spindle. A common problem, however, is that when the chuck nut is loosened from the spindle member in order to withdraw one bit and insert another, the loosened chuck nut can slip off the threaded portion of the spindle altogether, resulting in unwanted delay while the nut is recovered. Another problem is that accidental tightening of the chuck when a drill bit or bur is not engaged in the spindle can result in permanent damage to the threaded end of the spindle, rendering it unusable. Since the spindles are high-precision parts machined for spinning at high speeds, replacement is generally expensive.
As can be seen therefore, there is a need for a turbine or spindle assembly for a dental handpiece wherein the loosened chuck nut is physically retained on the spindle, and wherein accidental permanent deformation of the spindle is prevented when the chuck nut is tightened. The present invention satisfies these needs, as well as others, and overcomes the deficiencies found in currently available dental handpieces.